全文获取类型
收费全文 | 18452篇 |
免费 | 1666篇 |
国内免费 | 847篇 |
出版年
2024年 | 25篇 |
2023年 | 179篇 |
2022年 | 348篇 |
2021年 | 647篇 |
2020年 | 445篇 |
2019年 | 568篇 |
2018年 | 586篇 |
2017年 | 572篇 |
2016年 | 754篇 |
2015年 | 1152篇 |
2014年 | 1246篇 |
2013年 | 1443篇 |
2012年 | 1736篇 |
2011年 | 1621篇 |
2010年 | 1020篇 |
2009年 | 957篇 |
2008年 | 1108篇 |
2007年 | 1000篇 |
2006年 | 960篇 |
2005年 | 802篇 |
2004年 | 745篇 |
2003年 | 644篇 |
2002年 | 604篇 |
2001年 | 184篇 |
2000年 | 107篇 |
1999年 | 145篇 |
1998年 | 171篇 |
1997年 | 140篇 |
1996年 | 99篇 |
1995年 | 91篇 |
1994年 | 78篇 |
1993年 | 92篇 |
1992年 | 66篇 |
1991年 | 66篇 |
1990年 | 57篇 |
1989年 | 41篇 |
1988年 | 36篇 |
1987年 | 35篇 |
1986年 | 26篇 |
1985年 | 56篇 |
1984年 | 46篇 |
1983年 | 26篇 |
1982年 | 28篇 |
1981年 | 33篇 |
1980年 | 28篇 |
1979年 | 19篇 |
1978年 | 17篇 |
1977年 | 20篇 |
1976年 | 18篇 |
1973年 | 17篇 |
排序方式: 共有10000条查询结果,搜索用时 218 毫秒
271.
Maricela Apáez-Barrios José Alberto Salvador Escalante-Estrada Patricio Apáez-Barrios Yurixhi Atenea Raya-Montaño Juan Carlos Álvarez-Hernández 《Phyton》2021,90(4):1193-1203
Chickpea contains high levels of protein, vitamins and minerals. Acceptable chickpea yield is the result of meeting
nitrogen and phosphorus requirements. The effect of appropriately meeting such requirements reflects on growth
and can easily be evaluated using growth analysis. This research determined: (a) The effect of nitrogen and phosphorus fertilization on phenology, net assimilation rate, number of green leaves, leaf area, leaf area index and leaf
area duration; (b) Green chickpea yield and number of pods due to fertilization; and (c) The combination of
nitrogen and phosphorus fertilization that yields the most net revenue. Nitrogen and phosphorus fertilization
was evaluated; each at the doses of 0, 75 and 150 kg ha–1 (N0, N75, N150; P0, P75 and P150, respectively).
The combination of the levels of both nutrients generated nine combinations of treatments which were distributed in the field in a randomized complete block design in an arrangement of divided plots with four repetitions.
Timing of phenological phases were similar among treatments. Nitrogen and phosphorus fertilization increased
number of leaves, leaf area index, and leaf area duration that translated into increased green chickpea yield (GCY).
Combinations N150-P75 and N150-P150 produced the highest GCY. The highest net revenue and revenue per
peso invested was obtained with N150-P75. 相似文献
272.
273.
María Fátima Ladelfa Leticia Yamila Peche Gastón Ezequiel Amato Micaela Carolina Escalada Stefania Zampieri Franco Andrés Pascucci Andres Fernandez Benevento Dario Fernandez Do Porto Andrea Dardis Claudio Schneider Martin Monte 《Biochimica et Biophysica Acta (BBA)/Molecular Cell Research》2021,1868(7):119015
274.
In the present study, we explored the clinical and immunological characteristics of 575 uterine corpus endometrial carcinoma (UCEC) samples obtained from The Cancer Genome Atlas (TCGA) using the ESTIMATE and CIBERSORT algorithms. First, Kaplan–Meier and univariate Cox regression analyses indicated that the immune cell score was a prognostic factor for overall survival (OS) and recurrence-free survival (RFS). Multivariate Cox regression analysis further revealed that the immune cell score was an independent prognostic factor for UCEC patients. Second, we investigated the correlation between the infiltration levels of 22 types of immune cells and the immune score. Survival analysis based on the 22 immune cell types showed that higher levels of regulatory T cell, activated NK cell, and follicular helper T-cell infiltration were associated with longer OS, while higher levels of CD8+ T cell and naive B-cell infiltration were associated with longer RFS. Next, we performed differential expression and prognosis analyses on 1534 immune-related genes and selected five from 14 candidate genes to construct a prognostic prediction model. The area under the receiver-operating characteristic (ROC) curve (AUC) for 3- and 5-year survival were 0.711 and 0.728, respectively. Further validation using a stage I–II subgroup showed similar results, presenting AUC values for 3- and five-year survival of 0.677 and 0.692, respectively. Taken together, the present study provides not only a deeper understanding of the relationship between UCEC and the immune landscape but also guidance for the future development of UCEC immunotherapy. 相似文献
275.
Yongtao Sun Hai Feng Ting Zou Ming Hou Yanwu Jin Changping Gu Yuelan Wang Juan Li Mengjie Liu Min Zhang Yalei Gao 《Bioscience reports》2021,41(2)
Aim: To find out risk factors for postoperative cognitive dysfunction (POCD) after coronary artery bypass grafting (CABG), and to provide basis for clinical prevention of POCD. A total of 88 patients who underwent CABG were surveyed with Telephone Questionnaire (TICS-M) for their cognitive impairment after 3, 7, 21, 90, 180 days post-surgery. The occurrence of POCD was diagnosed by Neuropsychological Battery which included Vocabular Learning Test (VLT), Wisconsin Card Sorting Test (WCST), Trail Making Test (TMT) and Symbol Digit Modalities Test (SDMT). The preoperative, intraoperative and postoperative risk factors were assessed by the χ2 or t test. Multivariate analysis was used to study the correlation between the risk factors and the occurrence of POCD. Age, aortic plaque, carotid artery stenosis, cerebrovascular disease, anesthesia time, the rate of decline in intraoperative hemoglobin concentration (ΔHb) and systemic inflammatory response syndrome (SIRS) score on postoperative day 2 had statistically significant (P<0.05) influence on the occurrence of POCD. Aortic plaque, carotid artery stenosis, anesthesia time and SIRS score (odds ratio (OR) value > 1, P<0.05) are the risk factors for POCD. The incidence of day-21 and -180 POCD was approximately 26.1 and 22.7%, respectively. 相似文献
276.
277.
Zhuowen Su Shulin Cai Jianbin Liu Juan Zhao Ya Liu Junyu Yin Dianpeng Zhang 《Indian journal of microbiology》2021,61(2):160
Asparagus (Asparagus officinalis L) is an economically important crop, rich in nutrients, and is also conducive to solving ecological and environmental problems. Plants may acquire benefits from root-associated endophytic bacteria. However, the composition of the endophytic bacterial community associated with the roots of asparagus is poorly elucidated. In this study, the nine root samples of asparagus from three different varieties including Asparagus officinalis var. Grande (GLD), A. officinalis var. Jinglvlu3 (JL3) and A. officinalis var. Jingzilu2 (JZL) were investigated by high-throughput sequencing technology of the 16S rDNA V5-V7 hypervariable region of endophytic bacteria. A total of 16 phyla, 29 classes, 90 orders, 171 families, and 312 genera were identified. Endophytic bacteria diversity and bacteria structure was different among the three varieties and was influenced by rhizosphere soil properties and varieties. In the GLD variety, the main phyla were Proteobacteria, Actinobacteria, and Firmicutes. The main phylum in JL3 and JZL varieties was Proteobacteria. The observations showed that GLD had the highest diversity of endophytes as indicated by the Shannon index (GLD > JZL > JL3). The order of the endophytes richness was GLD > JL3 > JZL. The PCA and PCoA analysis revealed the microbial communities were different between three different asparagus varieties, and the microbial composition of GLD and JZL was more similar. This report provides an important reference for the study of endophytic microorganisms of asparagus. Supplementary informationThe online version contains supplementary material available at (10.1007/s12088-021-00926-6) contains supplementary material, which is available to authorized users. 相似文献
278.
279.
280.
Wang Zhen Huang Xu Liu Juan Xiao Feiyao Tian Miaomiao Ding Shenghua Shan Yang 《Biotechnology letters》2021,43(11):2161-2183
Biotechnology Letters - In this study, 44 flavone synthases (FNS) and flavonol synthases (FLS) from different origins were collected. The instability index and conserved domain of the enzymes were... 相似文献